Emergency lighting has been employed for several decades, for example to provide power to one or more light sources for illumination of the path of egress from a building or facility. Emergency lighting is required in industrial, commercial, and institutional buildings as part of the safety equipment. Emergency lighting relies on a limited backup power source for example a battery, to supply power to the light source(s). An emergency lighting unit (sometimes referred to as an “emergency ballast”) is designed to energize the light source(s) exclusively during periods of AC power failure when the ballast is said to be in “emergency mode” (EM), and may be combined with a conventional lighting unit (sometimes referred to as an “AC ballast”). The emergency lighting unit may sense the absence of the AC power and use the backup power source and dedicated electronic circuitry to energize the light source(s) during a limited period of AC power failure. In the USA, the required emergency lighting period is at least 90 minutes, while in Europe, e.g., it is 180 minutes, during which the emergency illumination level should not decline to under 60% of the initial level, as set for battery-powered emergency lighting systems by the life safety codes (e.g., section 7.2 of NFPA-101 and NEC 700.12).
Recently, light-emitting diodes (LEDs) have become more prominent in the market as a main light source for an occupied space. LEDs offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. These advantages are leading to the introduction of LEDs into a wide variety of applications and context. In particular, LED light sources are now being developed for use in emergency lighting systems.
Since life safety codes in the United States and Europe require that the emergency lighting unit sense the absence of AC power and use the backup power source and dedicated electronic circuitry to energize the light source(s) during a limited period of AC power failure, it becomes critical to have the ability to periodically test the status and functioning of the emergency lighting unit. In the United States, for example, NFPA-101 requires a functional test of the emergency lighting unit every 30 days for a minimum of 30 seconds, and once a year for 90 minutes. Owners must also keep written records of visual inspections and tests for inspection.
Typically, the emergency lighting is manually tested by a user, which may be an owner or employee of the facility or building walking around to every emergency lighting unit to perform the test. Alternatively, the test is performed by a technician who is hired specifically for testing. Following testing, proper records must be maintained for review and inspection. As a result, monthly and annual testing of emergency lighting unit is both time-consuming and expensive. Additionally, testing is often neglected or forgotten until an emergency state arises.
Further, although some existing emergency systems are able to perform self-testing, they rigidly perform this testing regardless of the current status of the lighting unit. The self-testing performed by these emergency systems can therefore cause a disruption if the space is occupied and the lighting unit is active.
Thus, there is a need in the art to provide an emergency lighting system that performs automated self-testing only when there is no AC power being supplied to the light sources.